An efficient and practical preparation of a potent low-affinity na+-dependent glucose cotransporter (SGLT2) inhibitor, sergliflozin etabonate

Article abstract of DOI:10.3987/COM-16-13484

The development of an efficient and practical process for the preparation of Sergliflozin etabonate (1), a prodrug of a novel selective low-affinity Na⁺-dependent glucose cotransporter (SGLT2) inhibitor, Sergliflozin (2), is described. Its development required a suitable process for large-scale manufacturing. We established a chromatography-free approach for 2-[(4-methoxyphenyl)methyl]phenol (5), the efficient O-glycosylation of 5 with penta-O-acetyl-β-D-glucopyranose (7) without using a trichloroacetimidate intermediate (9), and efficient reaction conditions to introduce an ethoxycarbonyl group onto the primary alcohol of 2 with high selectivity. This process provided 1 with a 45% overall yield from anisole (10).

Full text of DOI:10.3987/COM-16-13484

HETEROCYCLES, Vol. 92, No. 9, 2016
1599
HETEROCYCLES, Vol. 92, No. 9, 2016, pp. 1599 - 1613. © 2016 The Japan Institute of Heterocyclic Chemistry
Received, 16th April, 2016, Accepted, 20th June, 2016, Published online, 11th July, 2016
DOI: 10.3987/COM-16-13484
AN EFFICIENT AND PRACTICAL PREPARATION OF A POTENT
+
LOW-AFFINITY Na -DEPENDENT GLUCOSE COTRANSPORTER
(
SGLT2) INHIBITOR, SERGLIFLOZIN ETABONATE
1
2
2
Masahiro Kobayashi, * Hidetoshi Isawa, Junichi Sonehara, and Minoru
Kubota2
1
Head Office, Kissei Pharmaceutical Co., Ltd., 19-48 Yoshino, Matsumoto-City,
2
Nagano-Pref. 399-8710, Japan. Process Chemistry R&D, Kissei Pharmaceutical
Co., Ltd., 197-5 Kamiyoshi, Kubiki-ku, Joetsu-City, Niigata-Pref. 942-0145,
Japan. E-mail: masahiro_kobayashi@pharm.kissei.co.jp
Abstract – The development of an efficient and practical process for the
preparation of Sergliflozin etabonate (1), a prodrug of a novel selective
+
low-affinity Na -dependent glucose cotransporter (SGLT2) inhibitor, Sergliflozin
(
2), is described. Its development required a suitable process for large-scale
manufacturing. We established chromatography-free approach for
-[(4-methoxyphenyl)methyl]phenol (5), the efficient O-glycosylation of 5 with
a
2
penta-O-acetyl-β-D-glucopyranose (7) without using a trichloroacetimidate
intermediate (9), and efficient reaction conditions to introduce an ethoxycarbonyl
group onto the primary alcohol of 2 with high selectivity. This process provided 1
with a 45% overall yield from anisole (10).
INTRODUCTION
Recently, low-affinity Na -dependent glucose cotransporter (SGLT2) inhibitors have been developed.1
+
Two types of SGLT are known, SGLT1 and SGLT2; both act as transmembrane glucose transporters.
+
Although SGLT1 (the high-affinity Na -dependent glucose cotransporter) is expressed to some extent in
the kidney and contributes to glucose reabsorption, it is primarily expressed in the small intestine where it
plays an important role in glucose absorption.2,3 SGLT2 is specifically expressed in the kidney and
plays an important role in renal glucose reabsorption in the proximal tubule.4
Serglifrozin (2), discovered at Kissei Pharmaceutical Co., Ltd., exhibits an inhibitory activity that is
highly selective for SGLT2.

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HETEROCYCLES, Vol. 92, No. 9, 2016
6
-O-Ethoxycarbonyl-2-[(4-methoxyphenyl)methyl]phenyl-β-D-glucopyranoside (Sergliflozin etabonate
(1); Figure 1), a prodrug of 2, is metabolized to its active form 2 in the body, and may therefore be useful
as a preventative or therapeutic agent for diseases attributable to hyperglycemia, such as diabetes,
complications related to diabetes, and obesity.5-8 Larger quantities of 1 must now be provided for
preclinical and clinical evaluation as an antidiabetic agent. In this paper, we describe an efficient
process for the preparation of 1.
OMe
O
O
O
EtO
O
HO
OH
OH
Sergliflozin etabonate (1)
Figure 1
RESULTS AND DISCUSSION
Our initial synthetic route of Serglifrozin etabonate (1) in early development consisted of six steps,
including synthesis of tetra-O-acetyl-D-glucopyranosyl trichloroacetimidate (9), as shown in Scheme 1
and Scheme 2.
OMe
OH
OMe
(a)
(b)
+
Cl
OH
3
4
5
OMe
OMe
(c)
(d)
O
O
O
O
1
AcO
AcO
HO
HO
OAc
OH
OAc
OH
6
2
Reagents: (a) LiOH࣭H
2
O, benzene, reflux (30%); (b) 9, BF
3
࣭OEt , EtOAc, rt (77%); (c) NaOMe,
2
MeOH, 50 °C (73%); (d) ethyl chloroformate, 2,6-lutidine, acetone, 15 °C (66%).
Scheme 1

HETEROCYCLES, Vol. 92, No. 9, 2016
1601
HN
CCl3
O
OAc
OAc
O
OH
AcO
AcO
AcO
AcO
(a)
(b)
O
O
AcO
AcO
OAc
OAc
OAc
OAc
OAc
7
8
9
Reagents: (a) N,N-dimethylethylenediamine, THF, 20 °C (not isolated); (b) trichloroacetonitrile,
2
K CO
3
, EtOAc, 40 °C (crude product was used in the O-glycosylation step).
Scheme 2
The first step is the coupling reaction of phenol (3) and 4-methoxybenzyl chloride (4) in the presence of
lithium hydroxide monohydrate (LiOH·H O) to provide the aglycon 5 in a 30% yield following
2
chromatographic purification (Scheme 1). We prepared 9 separately by mono-deacetylation of
penta-O-acetyl-β-D-glucopyranose (7) with N,N-dimethylethylenediamine in THF followed by reaction of
the crude product of 8 with trichloroacetonitrile in the presence of potassium carbonate (K
acetate (EtOAc) (Scheme 2). Next, we carried out glycosylation of 5 with 9 in the presence of boron
trifluoride diethyl etherate (BF ·OEt ) in EtOAc to produce 6 in a 77% yield. The obtained 6 was
2
CO
3
) in ethyl
3
2
deacetylated with sodium methoxide (NaOMe) in MeOH to produce Serglifrozin (2) in a 73% yield, and
reaction of the isolated 2 with ethyl chloroformate in the presence of 2,6-lutidine in acetone provided 1 in
a 66% yield. The overall yield from 3 was 11%. While this route was capable of supplying small
amounts of 1, it suffered from several disadvantages.
The coupling reaction between 3 and 4 provided the aglycon 5 in low yield (30%); thus, chromatographic
purification was required to obtain highly pure 5. The trichloroimidation reaction of 8 is too hazardous
for large-scale manufacturing, because an excess amount of trichloroacetonitrile, a volatile and highly
toxic reagent, is required to obtain the trichloroacetimidate 9. Furthermore, 9 is too unstable to use
conveniently in large-scale manufacturing. Trichloroacetamide, a sublimation compound, is formed as a
by-product from the glycosylation of 5 with 9. Thus, the vacuum line and the vacuum pump of the
manufacturing equipment would be polluted by trichloroacetamide.
Because of these issues, this synthetic method is unsuitable for large-scale manufacturing. Therefore,
we investigated alternative processes for the preparation of 1, suitable for large-scale manufacturing.
An improved synthetic method for 1 was achieved in a five-step procedure without purification of 6
(intermediate), as shown in Scheme 3.

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HETEROCYCLES, Vol. 92, No. 9, 2016
OMe
Cl
OMe
OMe
OMe
(a)
(b)
+
O
OH
O
OH
1
0
11
12
5
OMe
OMe
(c)
(d)
(e)
O
O
O
O
1
AcO
HO
AcO
OAc
HO
OH
OAc
OH
6
2
Reagents: (a) AlCl
Et N, toluene, 40 °C; (d) NaOMe, MeOH, 15 °C (80% from 5); ethyl chloroformate, 2,6-lutidine,
pyridine, acetone, 0 °C (82%).
3
, PhCl, 110 °C (78%); (b) 10% Pd/C (wet), H
2
, EtOH, rt (88%); (c) 7, BF
3
࣭OEt ,
2
3
Scheme 3
The Friedel-Crafts acylation of anisole (10) with 2-methoxybenzoyl chloride (11) in the presence of
aluminum chloride (AlCl ) at 110 °C provided benzophenone (12), which was selectively demethylated
on the methoxy group at the 2-position. The crude product of 12 was crystallized from MeOH to
provide highly pure 12 in a 78% yield. Hydrogenation of 12 in EtOH with 0.3–0.4 MPa H at room
3
2
temperature in the presence of 10% Pd/C provided 5. The crude product of 5 was crystallized from
toluene/n-heptane to provide highly pure 5 in an 88% yield.
The key step of the synthesis was the formation of the O-glycosylated product 6. In the initial synthesis,
it was necessary to isolate 6 to remove trichloroacetamide. Consequently, 2 was provided in a 56%
yield from 5. To obtain 6 efficiently without using the trichloroacetimidate (9), we evaluated several
conditions for the direct O-glycosylation of 5 with 7. The results are summarized in Table 1. The
O-glycosylation of 5 with 7 (200 mol%) in the presence of boron trifluoride diethyl etherate (BF
3
·OEt ;
2
100 mol%) in dichloromethane (DCM) at room temperature provided the crude product of 6 with a good
yield (80%) and β-selectivity (94/6), and then the deacetylation of the crude product of 6 in the presence
of sodium methoxide (NaOMe) in MeOH proceeded almost quantitatively to provide 2 in a 71% isolated
yield from 5 (run 1). Using this method, it was not necessary to isolate 6 because the excess amount of
7
was converted to glucose and removed to the aqueous layers in the deacetylation step. Use of DCM is
undesirable for large-scale manufacturing because quenching of O-glycosylation with water is highly
exothermic and washing of the DCM layer with water is a complicated procedure. Additionally, it is
strongly desirable to avoid using DCM in a manufacturing process due to environmental issues. For the

HETEROCYCLES, Vol. 92, No. 9, 2016
1603
reasons mentioned above, we attempted to use toluene as an alternative solvent. The O-glycosylation in
the presence of BF ·OEt (100 mol%) in toluene at 30 °C did not proceed completely, and the yield of 6
3
2
was lower than run 1 (run 2). We concluded that the lower solubility of 7 in toluene, compared with
DCM, caused the low yield. Because it was difficult to increase the amount of toluene from the
perspective of manufacturing efficiency, we tried to improve its solubility by optimizing the reagent
equivalent. Fortunately, we found that an excess amount of BF
toluene, and using 300 mol% of BF ·OEt in toluene provided 6 in a good yield (80%), similar to that
when using DCM (run 3). In contrast, reducing the amount of 7 provided 6 in an insufficient yield, and
was consequently provided in a lower yield (60%) (run 4). To achieve higher β-selectivity and an
increased yield, triethylamine (Et N) was added to the O-glycosylation of 5 with 7 in the presence of
BF ·OEt N (30 mol%) at 30 °C resulted in both
, according to the method of Lee et al.9 Addition of Et
higher yield (89%) and higher β-selectivity (97/3) to provide 2 with a 79% isolated yield (run 5).
Increasing the amount of Et N to 60 mol% at 30 °C resulted in a lower yield (85%) of 6 compared with
run 5, and the yield of 2 decreased (74%) (run 6). Increasing the reaction temperature to 40 °C in the
presence of 60 mol% of Et N achieved the best results for both high yield (90%) and high β-selectivity
99/1) to provide 2 in an 80% yield (run 7).
3
·OEt enhanced the solubility of 7 in
2
3
2
2
3
3
2
3
3
3
(
Table 1. Optimization of O-glycosylation of 5 with 7
OMe
OMe
OMe
O
OAc
OAc
AcO
+
O
O
O
O
AcO
AcO
AcO
HO
HO
OH
OAc
OAc
OH
OAc
OH
5
7
6
2
6
2
run 7 (mol%) BF
3
·OEt
2
(mol%)
Base (mol%)
Solvent
Temp (°C)
yield (%)a) Ratio (β/α)b) Isolated yield (%)
1
2
3
4
5
200
200
200
150
200
100
100
300
300
300
none
none
none
none
DCM
rt
80
74
80
73
89
94/6
92/8
92/8
90/10
97/3
71
62
71
60
79
toluene
toluene
toluene
toluene
30
30
30
30
Et
Et
Et
3
3
3
N (30)
N (60)
N (60)
6
7
200
200
300
300
toluene
toluene
30
40
85
90
98/2
99/1
74
80
a) Determined by HPLC. Area % of product 6.
b) Determined by HPLC.

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HETEROCYCLES, Vol. 92, No. 9, 2016
Scheme 4 provides an explanation for the high β-selectivity. It is well-known that the glycosylation of
phenol derivatives with 7 provides β-glucosides as major products, because the attack of a phenolic
oxygen on the oxonium intermediate 13 takes place kinetically from the equatorial site. In the absence
of Et
3
N, interconversion to some extent of the kinetically stable eq-14 into the thermodynamically stable
ax-14 occurs during the glycosylation reaction, and the formation of thermodynamically more stable
α-glucoside causes lower β-selectivity. In the presence of Et N, the proton is rapidly removed from
3
eq-14 to provide β-glucoside at a higher selectivity.10
Scheme 4
To complete the synthesis, we optimized the ethoxycarbonylation condition of 2. Yamamoto et al.
reported that a sterically hindered amine was suitable for the selective acylation of the primary alcohols.11
The 6-O-ethoxycarbonyl derivative 1 was prepared by treatment of 2 with ethyl chloroformate in the
presence of 2,6-lutidine as a sterically hindered amine. In the initial synthesis, the reaction of 2 with
ethyl chloroformate (125 mol%) in the presence of 2,6-lutidine (175 mol%) in acetone at 15 °C for 23 h
provided 1 in a 66% isolated yield and ratio 1/bis-ethoxycarbonylated derivatives (2,6-, 3,6-, and

HETEROCYCLES, Vol. 92, No. 9, 2016
1605
4
,6-bis-O-ethoxycarbonyl derivatives) of 78/22 (Table 2, run 1). However, the required reaction time
fluctuated from several hours to 23 h. We investigated the cause of this fluctuation and found that the
content of 3-picoline as an impurity of 2,6-lutidine varied from 0.06% to 0.6%, and the different
contained quantities of 3-picoline affected the reaction time. Specifically, the reaction was accelerated
dramatically by the addition of a small amount of 3-picoline, which required lower reaction temperatures
and considerably shorter reaction times, and thus, the reaction was completed with a smaller amount of
ethyl chloroformate. The reaction of 2 with ethyl chloroformate (115 mol%) in the presence of
2,6-lutidine (150 mol%) and 3-picoline (2.4 mol%) at 0 °C proceeded completely in 4 h and achieved
high 1/bis-ethoxycarbonylated derivative selectivity (90/10), to provide 1 in an 80% yield (run 2). The
addition of pyridine was more effective than the addition of 3-picoline, and the reaction was completed in
2
h (82% yield, run 3). In contrast, the reaction using pyridine as a base provided 1 in a low yield (52%)
because of a significant amount of recovered 2 and the production of some by-products (run 4).
Table 2. Optimization of Ethoxycarbonylation of 2
OMe
OMe
O
O
O
HO
HO
O
O
EtO
O
OH
HO
OH
OH
OH
2
1
Base
Additive
ClCO
2
Et
Temp.
(°C )
Time
Ratio
1
run
(
mol%)
(mol%)
(mol%)
(h)
(1/Bis-ethoxycarbonylated derivatives)a) b) (% yield)
1
2
3
4
2,6-lutidine (175)
none
125
115
115
110
15
0
23
4
78/22
90/10
91/9
66
80
2,6-lutidine (150) 3-picoline (2.4)
2,6-lutidine (150)
pyridine (130)
pyridine (2.4)
none
0
2
82
0
1
81/19
52c)
a) Determined by HPLC.
b) Bis-ethoxycarbonylated derivatives contained 2,6-, 3,6- and 4,6-bis-O-ethoxycarbonyl derivatives.
c) Isolated by column chromatography.
The proposed mechanism for the reaction is shown in Scheme 5. 2,6-Lutidine did not form acyl
pyridinium salt with ethyl chloroformate because of steric hindrance from the 2,6-dimethyl groups.
2,6-Lutidine acted as a scavenger of hydrogen chloride. The addition of a catalytic amount of pyridine
formed the acyl pyridinium salt 15, which is a more reactive species than ethyl chloroformate, and the
reaction was accelerated.

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HETEROCYCLES, Vol. 92, No. 9, 2016
Scheme 5
In conclusion, we overcame the disadvantages of the initial synthetic route of 1, and developed an
efficient and practical process for the large-scale preparation of Sergliflozin etabonate (1). The benefits
of our new process are: 1) a chromatography-free approach to obtain highly pure 5; 2) a high yield and
high β-selective O-glycosylation of 5 with 7; 3) avoidance of highly toxic reagents such as
trichloroacetonitrile, unstable intermediates such as trichloroacetimidate (9), and halogenated solvents
such as DCM; and 4) an efficient ethoxycarbonylation condition onto the primary alcohol of 2 with high
selectivity by the addition of a catalytic amount of pyridine.
The results revealed that the optimized process described here improved the overall yield of the synthesis
of 1 from 11% to 45%.
EXPERIMENTAL
All melting points were determined using a Yanagimoto melting point apparatus and are uncorrected.
Optical rotations were recorded on a JASCO P-2300 polarimeter. IR spectra were recorded on a Nicolet
1
13
AVATAR 320 FT-IR spectrometer. H and C-NMR spectra were recorded on a Bruker AV-400M
400 MHz) or DRX-500 (500 MHz) spectrometer using TMS as the internal standard. High-resolution
(
MS spectra were recorded on an Agilent Technologies QToF 6520 mass spectrometer. HPLC analysis
was carried out using a Shimadzu 10A-VP.
Initial synthetic procedures
2
-[(4-Methoxyphenyl)methyl]phenol (5). The mixture of LiOH·H O (210 mg, 5.0 mmol) and phenol
2

HETEROCYCLES, Vol. 92, No. 9, 2016
1607
(3) (471 mg, 5.0 mmol) in benzene (3 mL) was refluxed for 1 h. 4-Methoxybenzyl chloride (4) (882 mg,
5.25 mmol) was then added to the reaction mixture. The mixture was refluxed with stirring for an
additional 3 h and then cooled to room temperature. Water (3 mL) and EtOAc (10 mL) were added to
the reaction mixture, and the biphasic solution was transferred to a separating funnel for phase separation.
The organic layer was dried over Na
residue was purified by silica gel chromatography (eluent EtOAc:n-hexane, 1/7) to provide 5 (323 mg,
0% yield), which was identified using NMR spectra compared with reference data.12 1H-NMR
CDCl ) δ: 3.78 (3H, s), 3.93 (2H, s), 4.66 (1H, s), 6.77–6.91 (4H, m), 7.10–7.15 (4H, m).
2
SO
4
and the filtrate concentrated under reduced pressure. The
3
(
3
Tetra-O-acetyl-D-glucopyranosyl trichloroacetimidate (9). N,N-Dimethylethylenediamine (63.4 g,
.719 mol) was added to a solution of penta-O-acetyl-β-D-glucopyranose (7) (200 g, 0.512 mol) in a
0
mixed solvent of EtOAc (400 g) and THF (400 g). The reaction mixture was stirred at 20 °C overnight.
EtOAc (200 g) and an aqueous solution of 15% phosphoric acid (607 g) were added to the reaction
mixture, and the biphasic solution was transferred to a separating funnel for phase separation. The
organic layer was washed successively with an aqueous solution of 10% NaCl (400 g), an aqueous
solution of 5% NaHCO
dried over Na SO and the filtrate concentrated under reduced pressure. The residue was then dissolved
in EtOAc (400 g). The solution was concentrated under reduced pressure to provide 8 as an oil. The
residue was dissolved in EtOAc (500 g). Trichloroacetonitrile (298 g, 2.06 mol) and K CO (10.9 g,
8.9 mmol) were added to the EtOAc solution of 8. The reaction mixture was stirred at 40 °C for 7 h
3
(400 g), and an aqueous solution of 18% NaCl (196 g). The organic layer was
2
4
2
3
7
and then aged at 20 °C overnight. Inorganic salt was removed by filtration through Celite, and the filter
cake was washed with EtOAc (400 g). The filtrate was concentrated under reduced pressure, and the
residue was dissolved in EtOAc (400 g). The solution was concentrated under reduced pressure. The
obtained residue was dissolved in EtOAc (200 g) to provide 9 as an EtOAc solution. The solution was
1
used in the next step without further purification. 9 was identified using H-NMR spectra compared
with reference data.13 1H-NMR analysis indicated an α-amoner/β-anomer ratio of 1/4. 1H-NMR
(
CDCl
.25–4.35 (1H, m), 5.10–5.25 (2H, m), 5.50–5.65 (1H, m), 6.56 (1H, d, J=3.5 Hz), 8.70 (1H, s);
1H-NMR (CDCl
) (β-amoner) δ: 2.02 (3H, s), 2.03 (3H, s), 2.04 (3H, s), 2.09 (3H, s), 3.85–3.95 (1H, m),
.10–4.20 (1H, m), 4.25–4.35 (1H, m), 5.15–5.35 (3H, m), 5.85–5.95 (1H, m), 8.72 (1H, s).
3
) δ: (α-amoner) δ: 2.02 (3H, s), 2.04 (3H, s), 2.05 (3H, s), 2.08 (3H, s), 4.10–4.25 (2H, m),
4
3
4
2-[(4-Methoxyphenyl)methyl]phenyl-2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside (6). EtOAc was
added to the EtOAc solution of crude 9, and the weight was adjusted to 630 g. 5 (67.0 g, 313 mmol)
was added to the solution, and a solution of BF ·OEt (13.4 g, 94.4 mmol) in EtOAc (130 g) was then
3
2

1608
HETEROCYCLES, Vol. 92, No. 9, 2016
added at 20 °C. The reaction mixture was stirred at 40 °C for 2 h and then cooled to 20 °C. An
aqueous solution of 18% NaCl (268 g) was added to the reaction mixture and the biphasic solution
transferred to a separating funnel for phase separation. The organic layer was washed successively with
an aqueous solution of 18% NaCl (268 g × 3), a solution of NaHCO
3
(3.4 g) and NaCl (24 g) in water
SO and
(170 g), and an aqueous solution of 18% NaCl (268 g). The organic layer was dried over Na
2
4
the filtrate concentrated under reduced pressure. EtOAc was added to the residue, and the weight was
adjusted to 402 g. MeOH (469 g) was added, and the resulting slurry was heated to 40 °C to dissolve
solids. The solution was cooled to 28 °C and seeded with 6. The solution was aged for 1.5 h at 28 °C,
during which time the product began to crystallize. The slurry was cooled to 20 °C and then stirred for 1
h at 20 °C. The slurry was cooled to 0 °C and then stirred for 1 h at 2 °C. The slurry was filtered, and
the wet cake was washed with MeOH (80 g × 2). The precipitate was dried in vacuo at 70 °C to give
2
0
-1
1
1
3
31 g (77% yield) of 6 as a white solid. mp 116–117 °C. [α] -29.7 (c 1.0, DMSO). IR (KBr) cm :
D
744, 1512, 1493, 1368, 1239. 1H-NMR (CDCl
) δ: 1.91 (3H, s), 2.03 (3H, s), 2.05 (3H, s), 2.07 (3H, s),
3
.77 (3H, s), 3.85–3.89 (3H, m), 4.17 (1H, dd, J=2.5, 12.4 Hz), 4.28 (1H, dd, J=5.5, 12.3 Hz), 5.11 (1H, d,
J=7.6 Hz), 5.18 (1H, t, J=9.5 Hz), 5.27–5.37 (2H, m), 6.78–6.82 (2H, m), 6.97–7.08 (5H, m), 7.14–7.19
(
(
1H, m). 13C-NMR (CDCl
d), 72.0 (d), 72.9 (d), 99.1 (d), 113.82 (d×2), 115.1 (d), 123.4 (d), 127.3 (d), 129.9 (d×2), 130.7 (d),
3
) δ: 20.5 (q), 20.6 (q×2), 20.7 (q), 34.3 (t), 55.2 (q), 62.0 (t), 68.4 (d), 71.1
1
31.4 (s), 132.4 (s), 154.5 (s), 157.9 (s), 169.2 (s), 169.4 (s), 170.3 (s), 170.6 (s). HRMS (ESI) m/z:
62.2288 [M+NH 36NO11: 562.2283).
]+ (Calcd for C28
5
4
H
2-[(4-Methoxyphenyl)methyl]phenyl-β-D-glucopyranoside (2). A methanolic solution of 1% NaOMe
(13.5 g, 2.5 mmol) was added to a suspension of 6 (27.2 g, 50 mmol) in a mixed solvent of EtOH (68 g)
and MeOH (27 g) at room temperature. The reaction mixture was stirred at 50 °C for 1 h and then
quenched by the addition of acetic acid (150 mg, 2.5mmol). EtOH (95 g) was added to the reaction
mixture at 50 °C. The solution was cooled to 35 °C and seeded with 2. The solution was aged for 1 h
at 35 °C, during which time the product began to crystallize. The solution was allowed to cool slowly
over 1 h to 3 °C and was stirred for 1.5 h at 3 °C. The slurry was filtered, and the wet cake was washed
successively with a mixed solvent of EtOH (27 g) and MeOH (5 g) and i-Pr
2
O (27 g). The precipitate
20
was dried in vacuo at 80 °C to give 13.8 g (73% yield) of 2 as a white solid. mp 112–113 °C. [α]D
42.4 (c 1.0, DMSO). IR (KBr) cm : 3363, 1513, 1491, 1453, 1301, 1238. 1H-NMR (DMSO-d
-
1
) δ:
.16–3.20 (1H, m), 3.25–3.35 (3H, m), 3.44–3.51 (1H, m), 3.70–3.73 (4H, m), 3.81 (1H, d, J=14.5 Hz),
.99 (1H, d, J=14.6 Hz), 4.56 (1H, t, J=5.8 Hz), 4.80 (1H, d, J=7.3 Hz), 5.01 (1H, d, J=5.3 Hz), 5.08 (1H,
-
6
3
3
d, J=4.8 Hz), 5.29 (1H, d, J=5.3 Hz), 6.79 (2H, m), 6.90 (1H, dt, J=1.3, 7.4 Hz), 7.06–7.15 (3H, m),
.18–7.22 (2H, m). 13C-NMR (DMSO-d
) δ: 34.0 (t), 54.9 (q), 60.7 (t), 69.8 (d), 73.4 (d), 76.7 (d), 77.0
7
6

HETEROCYCLES, Vol. 92, No. 9, 2016
1609
(d), 101.4 (d), 113.6 (d×2), 115.0 (d), 121.7 (d), 127.1 (d), 129.7 (d), 129.9 (d×2), 130.9 (s), 133.0 (s),
1
55.2 (s), 157.3 (s). HRMS (ESI) m/z: 394.1853 [M+NH
4
]+ (Calcd for C20
H28NO
7
: 394.1860).
6
-O-Ethoxycarbonyl-2-[(4-methoxyphenyl)methyl]phenyl-β-D-glucopyranoside
(1).
Ethyl
chloroformate (407 mg, 3.75 mol) was added drop-wise to the mixture of 2 (1.13 g, 3.0 mmol) and
2
,6-lutidine (563 mg, 5.25 mmol) in acetone (4 mL) while maintaining the temperature between 12 and
8 °C. The reaction mixture was stirred at 15 °C for 23 h. Water (5 mL) was added drop-wise while
1
maintaining the temperature below 30 °C, and EtOAc (10 mL) was then added to the mixture. The
biphasic solution was transferred to a separating funnel for phase separation. The aqueous layer was
extracted with EtOAc (5 mL). The EtOAc layers were combined, washed successively with an aqueous
solution of 10% citric acid (5 mL × 2), an aqueous solution of 10% NaCl (5 mL), an aqueous solution of
5% NaHCO
3
(5 mL × 2), and an aqueous solution of 10% NaCl (5 mL). They were then dried over
Na SO and the filtrate was concentrated under reduced pressure. EtOH was added to the residue, and
2
4
the weight was adjusted to 7.2 g. The mixture was heated to 65 °C to dissolve solids. The solution was
cooled to 55 °C and seeded with 1. The solution was aged for 1 h at 50 °C, during which time the
product began to crystallize. After the slurry was cooled to 25 °C, n-heptane (11 mL) was added
drop-wise to the slurry at 25 °C followed by stirring for 1 h at 25 °C. The slurry was cooled to 3 °C and
then stirred for 2 h at 3 °C. The slurry was filtered, and the wet cake was washed with a mixed solvent
of EtOH (1.5 mL) and n-heptane (3 mL). The precipitate was dried in vacuo at 70 °C to give 888 mg
2
0
-1
(
66% yield) of 1 as a white solid. [α] -43.5 (c 1.0, DMSO). IR (KBr) cm : 3495, 1744, 1514, 1488,
D
1
454, 1467, 1411, 1372, 1340, 1266. 1H-NMR (CDCl
Hz), 3.46–3.54 (3H, m), 3.56–3.61 (2H, m), 3.72 (1H, d, J=2.1 Hz), 3.75 (3H, s), 3.82 (1H, d, J=15.5 Hz),
.03 (1H, d, J=15.5 Hz), 4.11–4.22 (2H, m), 4.42 (2H, d, J=3.8 Hz), 4.69 (1H, d, J=7.4 Hz), 6.79–6.83
2H, m), 6.97–7.02 (2H, m), 7.04–7.07 (2H, m), 7.15–7.22 (2H, m). 13C-NMR (CDCl
) δ: 14.2 (q), 36.1
3
) δ: 1.27 (3H, t, J=7.0 Hz), 2.00 (1H, d, J=1.6
4
(
(
(
3
t), 55.4 (q), 64.4 (t), 66.4 (t), 69.6 (d), 73.4 (d), 73.8 (d), 75.7 (d), 100.8 (d), 114.1 (d×2), 114.4 (d), 122.7
d), 128.0 (d), 129.2 (d×2), 130.0 (s), 131.1 (d), 133.4 (s), 155.2 (s), 155.4 (s), 157.8 (s). HRMS (ESI)
m/z: 466.2070 [M+NH
4
]+ (Calcd for C23
H
32NO : 466.2072).
9
Efficient and practical synthetic procedures
-Hydroxy-4’-methoxybenzophenone (12). 2-Methoxybenzoyl chloride (11) (78.9 g, 0.462 mol) was
added drop-wise to a mixture of AlCl (anhydrous) (67.8 g, 0.506 mol) and anisole (10) (50.0 g, 0.462
2
3
mol) in chlorobenzene (250 ml) maintaining the temperature between 0 and 10 °C. The reaction mixture
was stirred at 110 °C for 1.5 h and then cooled to room temperature. After the reaction mixture was
added drop-wise to the mixture of toluene (600 mL) and 4 M HCl (1500 mL), maintaining the

1610
HETEROCYCLES, Vol. 92, No. 9, 2016
temperature between 0 and 20 °C, the mixture was stirred at room temperature for 1.5 h. The resulting
insoluble material was removed by filtration through Celite, and the filter cake was washed with toluene
(
300 mL × 2). The biphasic filtrate was transferred to a separating funnel for phase separation. The
toluene layer was washed successively with water (750 mL), an aqueous solution of 10% K CO (750
mL), water (750 mL), and an aqueous solution of 20% NaCl (750 mL). The resulting organic layer was
dried over Na SO , and the filtrate was concentrated under reduced pressure. The residue was dissolved
2
3
2
4
in MeOH (315 mL) at 60 °C. The solution was seeded with 12 and stirred at 20 °C overnight. The
resulting slurry was further stirred at 0 °C for 2 h. The slurry was filtered, and the wet cake was washed
with n-heptane (100 mL × 2). The precipitate was dried in vacuo at 35 °C to give 82.2 g (78% yield) of
-1
1
2 as a yellow solid. mp 53 °C. IR (KBr) cm : 1625, 1590, 1507, 1484, 1458, 1336, 1301, 1255, 1224.
1H-NMR (CDCl
) δ: 3.90 (3H, s), 6.86–6.90 (1H, m), 6.98–7.02 (2H, m), 7.06 (1H, dd, J=0.9, 8.4 Hz),
.47–7.51 (1H, m), 7.63 (1H, dd, J=1.5, 7.9 Hz), 7.70–7.74 (2H, m), 11.98 (1H, s). 13C-NMR (CDCl
3
7
3
)
δ: 55.5 (q), 113.7 (d×2), 118.3 (d), 118.5 (d), 119.4 (s), 130.3 (s), 131.9 (d×2), 133.3 (d), 135.8 (d), 162.9
+
(
s×2), 200.1 (s). HRMS (ESI) m/z: 229.0873 [M+H] (Calcd for C14
H
13
O : 229.0859).
3
2-[(4-Methoxyphenyl)methyl]phenol (5). A solution of 12 (10 g, 0.0438 mol) in EtOH (50 mL) was
hydrogenated over 10% Pd-C (50% wet, 2.2 g) for 5 h at room temperature under 0.35 MPa of H . The
2
Pd-C was removed by filtration through Celite, and the filter cake was washed with EtOH (10 mL × 2).
The filtrate was concentrated under reduced pressure. The residue was dissolved in toluene (100 mL) at
50 °C. Activated carbon was added to the solution and stirred for 0.5 h. The activated carbon was
removed by filtration through Celite, and the filter cake was washed with toluene (10 mL × 2). The
filtrate was concentrated under reduced pressure. The residue was dissolved in toluene (40 mL) at 25 °C.
After the solution was seeded with 5, n-heptane (80 mL) was added drop-wise to the solution over a 0.2 h
period at 25 °C, during which time the product began to crystallize. The resulting slurry was stirred at
25 °C overnight and further stirred at 0 °C for 1 h. The slurry was filtered, and the wet cake was washed
with n-heptane (20 mL × 2). The precipitate was dried in vacuo at 40 °C to give 8.21 g (88% yield) of 5
as a yellow solid.
2
-[(4-Methoxyphenyl)methyl]phenyl-2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside (6).
100 g, 0.705 mol) was added drop-wise to the mixture of 5 (50.0 g, 0.233 mol),
penta-O-acetyl-β-D-glucopyranose (7) (182 g, 0.466 mol), and Et N (14.0 g, 0.138 mol) in toluene (460
mL), maintaining the temperature between 15 and 40 °C. The reaction mixture was stirred at 40 °C for
h and then cooled to 20 °C. The mixture was aged for 12 h at 10–30 °C. Water (200 mL) was added
drop-wise, maintaining the temperature below 40 °C, and the mixture was stirred at 40 °C until the
BF
3
·OEt
2
(
3
6

HETEROCYCLES, Vol. 92, No. 9, 2016
1611
resulting inorganic salts were dissolved. After cooling to 25 °C, the biphasic solution was transferred to
a separating funnel for phase separation. The toluene layer was washed successively with water (200
mL × 3), an aqueous solution of 5% NaHCO (100 g), and water (50 g). The toluene layer was
3
concentrated under reduced pressure. The residue was dissolved in MeOH (1 L) at 50 °C and then
cooled to room temperature. HPLC analysis indicated the yield of 6 was 90% (117 g).14 The solution
was used in the next step without further purification.
2
-[(4-Methoxyphenyl)methyl]phenyl-β-D-glucopyranoside (2). A methanol solution of 10% NaOMe
19.7 g, 0.0348 mol) was added drop-wise to the methanol solution of 6 from the preceding step,
maintaining the temperature between 23 and 27 °C. The reaction mixture was stirred for 1 h at
2–18 °C, and then the reaction was quenched by the addition of acetic acid (2.10 g, 0.0350 mol) in
(
1
MeOH (16 mL). The mixture was concentrated under reduced pressure. The residue was dissolved in
water (190 g) and EtOAc (490 mL) at 55 °C and then cooled to 35 °C. The biphasic solution was
transferred to a separating funnel for phase separation. The aqueous layer was extracted with EtOAc (70
mL). The EtOAc layers were combined and washed successively with water (130 g), an aqueous
solution of 10% NaCl (130 g), and water (130 g). The EtOAc layer was concentrated under reduced
pressure, and the residue was dissolved in EtOH (810 mL) at 70 °C. The solution was concentrated
under reduced pressure until more than 350 mL distillate was collected. EtOH was added to the residue,
and the weight was adjusted to 587 g. Water (17 g) was added, and the resulting slurry was heated to
70 °C to dissolve solids. The solution was cooled to 50 °C and seeded with 2. The solution was aged
for 1 h at 45 °C, during which time the product began to crystallize. The slurry was allowed to cool
slowly over 1 h to 3 °C and was stirred for 1.5 h at 3 °C. The slurry was filtered, and the wet cake was
washed successively with EtOH (160 mL) and i-Pr
2
O (180 mL). The precipitate was dried in vacuo at
8
0 °C to give 70.4 g (80% yield) of 2 as a white solid.
6
-O-Ethoxycarbonyl-2-[(4-methoxyphenyl)methyl]phenyl-β-D-glucopyranoside
(1).
Ethyl
chloroformate (21.6 g, 0.199 mol) was added drop-wise to the mixture of 2 (65.0 g, 0.173 mol),
,6-lutidine (27.8 g, 0.259 mol) and pyridine (0.33 g, 4.2 mmol) in acetone (210 mL), maintaining the
2
temperature between -1 and 5 °C. The reaction mixture was stirred at 0 °C for 2 h. The reaction was
monitored by HPLC.15 Water (200 mL) was added drop-wise, maintaining the temperature below 30 °C,
and then EtOAc (220 mL) was added to the mixture. The biphasic solution was transferred to a
separating funnel for phase separation. The aqueous layer was extracted with EtOAc (140 mL). The
EtOAc layers were combined, washed successively with an aqueous solution of 10% citric acid (180 mL
×
2), an aqueous solution of 10% NaCl (66 g), an aqueous solution of 5% NaHCO (65 g × 2), and an
3

1612
HETEROCYCLES, Vol. 92, No. 9, 2016
aqueous solution of 10% NaCl (100 g), and then dried over Na
2
SO
4
(65 g). After acetic acid (10 g,
0
.167 mol) was added to the filtrate, the mixture was concentrated under reduced pressure. The residue
was dissolved in EtOH (660 mL) at 65 °C. The solution was concentrated under reduced pressure until
more than 330 mL distillate had been collected. EtOH was added to the residue, and the weight was
adjusted to 370 g. n-Heptane (120 mL) was added, and the resulting slurry was heated to 65 °C to
dissolve solids. The solution was cooled to 55 °C and seeded with 1. The solution was aged for 1 h at
50 °C, during which time the product began to crystallize. n-Heptane (480 mL) was added drop-wise to
the slurry, maintaining the temperature between 50 and 60 °C, and the slurry was stirred for 0.5 h at 55 °C.
The slurry was allowed to cool slowly over 2.5 h to 30 °C, then cooled to 3 °C, and then stirred for 1.5 h
at 3 °C. The slurry was filtered, and the wet cake was washed with a mixed solvent of EtOH (80 mL)
and n-heptane (180 mL). The precipitate was dried in vacuo at 70 °C to give 63.6 g (82% yield) of 1 as
a white solid.
REFERENCES (AND NOTES)
1.
2.
3.
4.
5.
6.
W. N. Washburn, Expert Opin. Ther. Patents, 2009, 19, 1485.
A. M. Pajor and E. M. Wright, J. Biol. Chem., 1992, 267, 3557.
E. M. Wright, Am. J. Physiol. Renal Physiol., 2001, 280, F10.
Y. Kanai, W. S. Lee, G. You, D. Brown, and M. A. Hediger, J. Clin. Invest., 1994, 93, 397.
H. Fujikura, N. Fushimi, T. Nishimura, K. Tatani, and M. Isaji, PCT, WO 02/28872 (2002).
H. Fujikura, N. Fushimi, T. Nishimura, K. Tatani, K. Katsuno, M. Hiratochi, Y. Tokutake, and M.
Isaji, PCT, WO 01/688660 (2001).
7
.
K. Katsuno, Y. Fujimori, Y. Takemura, M. Hiratochi, F. Itoh, Y. Komatsu, H. Fujikura, and M. Isaji,
J. Pharmacol. Exp. Ther., 2007, 320, 323.
8
9
1
.
M. Isaji, Curr. Opin. Investig. Drugs, 2007, 8, 285.
.
S. Y. Lee, S. E. Rho, K. Y. Min, T. B. Kim, and H. K. Kim, J. Carbohydr. Chem., 2001, 20, 503.
0. M. Yamaguchi, A. Horiguchi, A. Fukuda, and T. Minami, J. Chem. Soc., Perkin Trans. 1, 1990,
079.
1
11. K. Ishihara, H. Kurihara, and H. Yamamoto, J. Org. Chem., 1993, 58, 3791.
12. I. T. Akimova, A. V. Kaminsky, and V. I. Svistunova, Chem. Heterocycl. Compd., 2005, 41, 1374.
13. B. N. Cook, S. Bhakta, T. Biegel, K. G. Bowman, J. I. Armstrong, S. Hemmerich, and C. R. Bertozzi,
J. Am. Chem. Soc., 2000, 122, 8612.
1
4. HPLC conditions: column, Inertsil ODS-3 (5 μm) 4.6 mm × 250 mm (GL Science Inc.); mobile
phase, isocratic elution with acetonitrile / 0.02 M KH
2
PO
4
, pH 3 = 6/4; flow rate, 1.0 mL/min;
column oven temperature, 40 °C; wave length, 225 nm; retention times, 5 = 16 min, α-anomer of 5 =

HETEROCYCLES, Vol. 92, No. 9, 2016
1613
1
8 min.
5. HPLC conditions: column, Inertsil ODS-3 (5 μm) 4.6 mm × 250 mm (GL Science Inc.); mobile
phase, gradient elution with 5 min 4/6 → 15 min 6/4 → 30 min 6/4 of acetonitrile/0.02 M KH PO
pH 3; flow rate, 1.0 mL/min; column oven temperature, 40 °C; wavelength, 225 nm; retention times,
= 17 min, 2,6- and 4,6-bis-O-ethoxycarbonyl derivatives = 24 min, 3,6-bis-O-ethoxycarbonyl
derivative = 25 min.
1
2
4
,
1